1. Field of the Invention
The present invention relates to pressure control in a resistance welder. More particularly, the present invention relates to pressure control of a tip dresser cutter at the time of dressing an electrode tip of a resistance welder. Further, the present invention relates to a pressure control method for dressing the electrode tips of numerous resistance welders with a single dressing pressure controller.
2. Background of the Invention
A method and equipment for dressing the electrode tip of a resistance welder, by changing the pressure of the electrode tip on the cutter of the tip dresser, has been proposed by the applicant of the present invention.
In this method and equipment, the following operations were performed: (1) at the time of setting the electrode tip to the dresser a comparatively weak force was used to press the electrode tip; (2) when the electrode tip came into contact with the dresser, the tip was worked with a strong force applied between the electrode tip and dresser; (3) at the time of finish-cutting a weak force, a force which was weaker than that used to cut the flank side, was used to press the electrode tip; and (4) burrs were removed at the time of cutting by fluctuating the tip.
By changing the pressure of the electrode tip exerted on the cutter while trim-cutting, it was possible to lower the impact force of the electrode tip on the cutter at the time of setting. In making the load on the cutter, etc. smaller the dressing finish of the electrode tip was improved.
In the past, the dressing pressure controller described above was installed in the resistance welder. Hence, not only was the resistance welder made larger, thus occupying a larger floor area, there was also a problem in that the unit price of the welding machine was made higher.
In addition, when multiple resistance welder units were connected to a single driving controller, operations of other resistance welders had to be stopped in order to dress the electrode tip of a single resistance welder. As a result, the availability of the resistance welders dropped.
In the case of a portable tip dresser equipped with a small-sized motor, the dresser was manually transported to the position of the electrode tip, the upper and lower electrode tips were urged to the rotating blade and, by rotating the rotary blade, the surface of both the electrode tips were simultaneously ground.
If, during the initial step of grinding, excessive pressure-contact force was applied to the electrode tip, problems such as excessive bite occurred resulting in damage to the rotating blade. Further, application of too much torque caused heating of the driving motor.
In addition if, after cutting, the rotating blade was stopped without releasing the pressure-contact force of the electrode tip, cutting burrs occurred on the surface of the electrode tip on which finishing had been completed.
The present invention overcomes the above-mentioned problems by providing a pressure controller and pressure control method which will not make the welder too large and too expensive. In accordance with the method of the present invention, even when multiple resistance welders are connected to a single driving controller, the dressing of an electrode tip only for the desired resistance welder, without stopping the working state of other resistance welders, is possible.
Another object of the present invention is to provide a heating controller and heating control method for the resistance welder that can prevent problems such as damage on the surface of the rotating blade and electrode tip. This object is achieved by performing a series of cutting operations to the electrode tips in relation to fitting operations of the tip dresser.
The following operations are performed to achieve the above-noted object: (1) at the time of dressing the electrode tip, the supply of the pressurized fluid to the pressurizing mechanism of the resistance welder is switched from the route used during ordinary welding to the route from the exclusive-use dressing pressure controller; (2) the dressing pressure controller controls the pressure; (3) by the same dressing pressure controller, the pressurizing force is controlled at the time of dressing the electrode tips of multiple resistance welders.